The present invention relates generally to electronic devices having surface mount lamps, and more particularly concerns circuit boards of the electronic devices using adhesive pads to secure the surface mount lamps to the circuit boards in automated assembly processing.
Electronic devices employing surface mount lamps are most commonly required in instrument clusters of vehicles. Typically, these devices are used to communicate to a user. These devices include, for example, climate controls, audio systems, and instrument panels for the speedometer and tachometer. The surface mount lamps within these electronic devices are typically about 6 mm square in size and 10 mm in height.
Currently, surface mount lamps are attached to circuit boards by soldering electric leads of the surface mount lamps to conductive pads integrally formed within the circuit boards. Typically, a surface mount lamp has two electric leads on opposing corners of its square base. These leads are soldered to two conductive pads integrally formed within a circuit board. Unfortunately, this technique does not properly secure the lamps to the circuit boards during automated assembly processing. The torque associated with the height of a typical lamp can be excessive for only two pads to hold the lamp to the circuit board. Consequently, the lamps can rock back and forth and move off the pads or completely fall off the circuit boards prior to a reflow process. To resolve this problem, manufacturers are forced to install the lamps in the last machine in the assembly process. This sequence in the assembly process compromises optimal performance of the process. Further, other problems occur post-reflow whereupon the lamps become detached from the circuit boards during vibration testing. The soldering of the electric leads to the conductive pads is not stable enough to provide precise placement within tolerance requirements for accurate lighting. Such adverse effects are obviously undesirable.
Therefore, a need exists for an electronic device that eliminates movement of a surface mount lamp and detachment of a surface mount lamp from a circuit board during and after the automated assembly process.
It is an object of the present invention to provide an apparatus and a method for attaching a surface mount lamp to a circuit board of an electronic device such that the surface mount lamp does not deviate beyond design tolerances or completely fall off the circuit board during automated assembly processing.
In accordance with the above and other objects of the present invention, an electronic device having a circuit board and surface mount lamps attached thereto is provided. For each surface mount lamp, the electronic device includes at least two conductive pads and at least two adhesive pads. Typically, the surface mount lamp has two electric leads on opposing corners of its base that are soldered to two conductive pads integrally formed in the circuit board. Preferably, these pads are circular so as to provide for optimal part centering and best paste release from the stencils. The conductive pads are typically copper or copper with a solder coating. A common diameter for a conductive pad is about 3.5 mm.
The adhesive pads are integrally formed within the circuit board and are used to reinforce the connection between the surface mount lamp and the circuit board. In a preferred embodiment, two adhesive pads are used to provide a solder connection between the circuit board and opposing corners of the lamp base which are not occupied by the two electric leads. Preferably, the adhesive pads are circular in order to allow for best paste release from the stencils. Similar to the conductive pads, adhesive pads are typically copper or copper with a solder coating. A common diameter for an adhesive pad is about 3.0 mm.
Surface mount lamps are attached to circuit boards during the component placement and reflow processes. During the component placement process, the lamps are placed into position such that the conductive pads are in contact with the electric leads and the adhesive pads engage opposing corners of the plastic base. The attachment between the surface mount lamp and the circuit board is completed during the reflow process wherein the electric leads are soldered to the conductive pads and the opposing corners of the plastic base are melted to the adhesive pads to form a firm attachment. In an alternative embodiment, the adhesive pads have a solder coating such that the adhesive pads are soldered to the opposing corners of the plastic base during the reflow process.
Additional objects and features of the present invention will become apparent upon review of the drawings and accompanying detailed description of the preferred embodiments.